1. Field of the Invention
This invention relates to power transmission belts and in particular to cross-grooved banded belts.
2. Description of the Background Art
In one conventional form of power transmission belt, a plurality of V-belt elements are retained in laterally spaced, parallel arrangement by a tie band. To provide improved flexibility in such tie band belts, transverse grooves have been provided in the distal portions of the V-belt elements. The present invention is concerned with an improved arrangement of the grooves of such a grooved banded belt manufacture.
More specifically, one form of cross-grooved banded belt is illustrated in U.S. Pat. No. 2,802,511 of Dale L. Waugh. As shown therein, the V-belt elements are provided with transverse grooves which alternate from rib to rib in a staggered manner. Waugh teaches that the grooves should be disaligned so as to provide a greater area of contact between the belt and pulley at any given instant than would be provided if the grooves all lay in transverse alignment.
Donald E. Clinkenbeard, in U.S. Pat. No. 3,564,933, shows a banded transmission belt wherein the V-belt elements are of the wrapped type and the tie band is provided with a bias cut reinforcing fabric.
K. V. Gentry shows, in U.S. Pat. No. 3,626,775, a V-belt element having longitudinally symmetrical notches.
In U.S. Pat. No. 3,853,017 of Jack D. White, Jr. et al, a power transmission belt is disclosed wherein the tie band is reinforced by a knitted fabric layer.
Delyn M. Stork discloses, in U.S. Pat. No. 3,948,113, a power transmission belt wherein the V-belt elements are provided with transverse grooves which are illustrated as being segmentally cylindrical.
In U.S. Pat. No. 4,011,766, Dale L. Waugh shows a power transmission belt similar to that of the Waugh U.S. Pat. No. 2,802,511 discussed above wherein the V-belt elements are provided with grooves which are staggered in the respective V-belt elements. The patentee again requires the staggered relation of the equal-sized teeth of the V-belt elements to assure that the belt is free of hinge points and points out that if the grooves were in transverse alignment between the V-belt elements, they would cause a reduced thickness hinge line to be formed in the belt which would weaken the belt.
One of the problems found in the grooved banded belts of the prior art is illustrated in FIGS. 1 and 2 of the drawing. Thus, as shown in FIG. 1, when such a transversely grooved banded belt is utilized for power transmission between a pair of pulleys, a number of different stresses and shearing forces are developed, tending to cause cracking of the belt, particularly from the root of the belt grooves, as illustrated in FIG. 2. As further shown in FIG. 1, a flexing of the belt occurs at the point where the belt leaves the driven pulley as the belt tends to remain in the annular grooves of the driven pulley both as a result of inertia and friction and, thus, is bent somewhat as it is pulled out of the grooves at a point beyond the tangent between the two pulleys, as illustrated in FIG. 1. This constant flexing of the belt at this point further tends to produce cracks, such as illustrated in FIG. 2. The proposed staggared arrangements of the belt grooves have not fully satisfactorily overcome the cracking problems and, thus, the different transversely grooved banded belts of the prior art have limited useful life.